Wire or rod (hereinafter termed "wire" only) is formed at high speed in a rolling or drawing mill and is delivered in straight condition to a coiler that forms it into a succession of large-diameter turns that it deposits on a surface, normally a conveyor of some type. Thence the coiled wire is moved through subsequent treatment steps such as heat treatment, descaling, pickling, or simply cooling. It is critical that the wire be deposited in uniformly shaped and spaced coils so that the subsequent treatment stage is effective.
The typical coiling system comprises a coiler head carrying a guide tube twisted in three dimensions and having an upstream end opening axially in line with an axis about which the head is rotated and a downstream end which opens at a location radially offset from the axis and directed generally tangentially. The straight wire is fed into the upstream end of the guide tube as the head is rotated about its axis so that as the wire passes through the tube it is bent into an arcuate shape and will fall in a coil when leaving the downstream end of the tube.
The guide tube is of uniform cross-section but starts at a location at the axis directed axially upstream and moves through a spiral to a location spaced well out from the axis and opening tangentially, so that it forms a complexly oriented offcenter mass between its ends. The tube is carried on the outer edge of a thin helical mounting plate having an inner edge secured on a helix on the support tube and an outer edge that diverges from the axis downstream and that is clipped to the guide tube. Obviously if the coil-laying head is rotated at high speed there will be considerable throw.
Accordingly it is standard practice to provide a plurality of counterweight blocks and/or several axially extending counterweight ribs on the support tube. Such arrangements make at best an approximation of uniform distribution of mass about the axis, creating some vibration at high speeds. Furthermore they are subject to deformation when in use and any offcenter problems are often aggravated.
In another known system a spiral rod mounted on a helical mounting plate is provided diametrally opposite the guide tube so as to offset its mass. Constructing such a counterweighted head is very difficult as the parts must be welded together and many of the seam areas are very difficult to get into. In addition this system is only partially effective since at high speeds the stiffening plates deform and allow their centers of mass to move somewhat, and the thermal expansion occurring during operation also causes deformations that displace the various centers of mass.